Cover plate for lighting fixture and lighting fixture having the same

ABSTRACT

Disclosed is a cover plate for a lighting fixture and a lighting fixture having the same, which achieves superior light diffusivity and light uniformity as well as superior light transmission in comparison with the prior art, thereby improving a luminance characteristic. The cover plate is arranged at an exterior of an light source of the light fixture so as to exit lighting emitted from the light source outward. The cover plate is made of light transmissive resin material having 5-35% of bubbles for light scattering, which has a diameter within a range of 60 μm˜700 μm, and exits light emitted from the light source while diffusing the light to the whole area of the cover plate.

TECHNICAL FIELD

The present invention relates to a cover plate for a lighting fixture,and more particularly to a cover plate for a lighting fixture, which isapplied to an advertisement fixture such as a billboard, an interiorlighting, or a lighting fixture for an interior design, etc. so as touniformly diffuse light emitted from an light source through all partsof the cover plate, thereby emitting the light at a high lighttransmission and with a high luminance.

BACKGROUND ART

Various advertisement fixtures, such as advertisement paper, billboards,and luminous advertisement fixtures, have been recently used inadvertising products of various companies or various businesses. Such anadvertisement fixture uses various kinds of pictures, phrases,photographs, patterns, etc., so as to increase recognition of desiredinformation to be communicated to a purchaser, and particularly, manykinds of advertisement fixtures using a lighting fixture have beendeveloped so as to make it possible to properly communicate desiredinformation to a purchaser at night time or at a place under lowillumination.

Generally, such an advertisement fixture using a lighting fixtureincludes a cover plate having transparent or semitransparent materialhaving light transmission. The cover plate exiting light emitted from anlight source, such as a fluorescent lamp or a lighting emitting diode(LED), etc., outward while diffusing the light, and also hides the lightsource. The cover plate may have a thin film engraved with a picture, aphrase, a pattern, etc. attached to a surface thereof, or may have itsown shape of a specific character or a picture, etc.

Also, in addition to an advertisement fixture, a lighting fixture, suchas a fluorescent lamp, a stand light, a street light, or a light for aninterior design, etc. employs a cover plate.

Most cover plates employed in a typical lighting fixture are generallymanufactured by adding polymeric particulates, to which inorganicparticles, styrene-based or acryl-based polymeric particles, etc. arepartially cross-linked.

However, the conventional cover plate has high specific gravity so thatits weight is heavy and much manufacturing cost is required. Also, theconventional cover plate has a superior optical diffusivity, but has alow light transmission, so there is a problem that aluminance-characteristic thereof is generally low.

Particularly, when an advertisement fixture becomes larger, the size ofa cover plate employed therein increases and the thickness thereof alsoincreases. However, when the thickness of a cover plate increases assuch, the number of corpuscles included therein also increases inproportion to the increases of thickness thereof. Accordingly, lighttransmission remarkably decreases so that luminance also notablydecreases.

DISCLOSURE Technical Problem

Accordingly, the present invention has been made to solve theabove-mentioned problems occurring in the prior art, and the presentinvention provides a cover plate for a lighting fixture and a lightingfixture using the same, which achieves superior light diffusivity andlight uniformity and also has superior light transmission in comparisonwith a conventional art, thereby improving a luminance-characteristic.

Technical Solution

In accordance with an aspect of the present invention, there is provideda cover plate for a lighting fixture, which is arranged at an exteriorof an light source of the lighting fixture so as to exit lightingemitted from the light source outward, wherein the cover plate is madefrom light transmissive resin material having 5˜35% of bubbles for lightscattering, so as to diffuse and emit light emitted from an light sourcethrough an entire surface of the cover plate.

In accordance with another aspect of the present invention, there isprovided a lighting fixture includes: a case; an light source installedat an interior of the case so as to emit light; and a cover plateinstalled at an outer side of the light source, the cover plate beingmade from light transmissive resin material including bubbles for lightscattering with an inclusion rate of 5˜35%, so that the cover plateexits light emitted from the light source while diffusing the light to awhole surface of the cover plate.

ADVANTAGEOUS EFFECTS

According to the present invention as described above, light emittedfrom an light source of a lighting fixture is scattered and refracted bybubbles of a cover plate so that the light is equally diffused throughthe whole surface of the cover plate, and is also refracted while beingtransmitted through the bubbles. Therefore, the degree of decrease oflight transmission is minimized so that a superiorluminance-characteristic can be provided.

DESCRIPTION OF DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 a perspective view illustrating an advertisement fixtureemploying a cover plate for a light fixture according to one embodimentof the present invention;

FIG. 2 is an exploded perspective view illustrating the advertisementfixture as shown in FIG. 1;

FIG. 3 is a sectional view illustrating the cover plate of theadvertisement fixture as shown in FIG. 1 and a main part of an lightsource, according to one embodiment of the present invention;

FIG. 4 is a picture photographed by an optical microscope showing astate of bubbles in a case where a bubble inclusion rate of a coverplate is less than 5%;

FIG. 5 is a picture photographed by an optical microscope showing astate of a bubble having a diameter of 65 μm among bubbles included in acover plate;

FIG. 6 is a picture photographed by an optical microscope showing abubble having a diameter of 750 μm among bubbles included in a coverplate;

FIG. 7 is a view illustrating a cover plate according to the secondembodiment of the present invention, similarly to FIG. 3;

FIG. 8 is a rear view illustrating a pattern formed on the cover plateas shown in FIG. 7, according to one embodiment;

FIG. 9 is a rear view illustrating a pattern formed on the cover plateas shown in FIG. 7, according to another embodiment;

FIG. 10 is a view illustrating a cover plate according to the thirdembodiment of the present invention, similarly to FIG. 3;

FIG. 11 is a view illustrating a modified cover plate according to thethird embodiment as shown in FIG. 10;

FIG. 12 is an exploded perspective view illustrating an advertisementfixture employing a cover plate for a lighting fixture according toanother embodiment of the present invention; and

FIG. 13 is a sectional view illustrating a main part of theadvertisement fixture as shown in FIG. 12.

BEST MODEL

Hereinafter, exemplary embodiments of a cover plate for a lightingfixture and a lighting fixture using the same according to the presentinvention will be described in detail with reference to the accompanyingdrawings.

Although a cover plate for a lighting fixture according to the presentinvention as described below has a flat square-shape, a cover plate fora lighting fixture according to the present invention may be variousshapes, such as a spherical shape, a cylindrical shape, apolyhedron-shape, etc., according to a characteristic of a lightingfixture in which the cover plate is employed.

Also, although a cover plate for a light fixture according to thepresent invention can be installed in such a manner that the cover plateis exactly arranged at an upper side of an light source of a lightfixture or surrounds the light source, a light guide plate exiting lightemitted from the light source to a facial light source can be arrangedat one side of the light source, and a cover plate can be also installedat an outer side of a light emitting surface of the light guide plate soas to diffuse the light.

FIGS. 1 to 3 are views illustrating an advertisement fixture employing acover plate for a lighting fixture according to one embodiment of thepresent invention.

With reference to FIGS. 1 and 2, the advertisement fixture includes acase 10 having one surface opened, an light source 20 installed at theinterior of the case 10, and a cover plate 30 assembled with the openedsurface of the case 10.

A light emitting surface of the front side of the cover plate 30 mayhave a film, a cloth, etc. engraved with a predetermined advertisementphrase, a pattern, a picture, etc. attached thereon, or may be coated bypaints having a predetermined color.

Although, according to this embodiment, the light source 20 includes atleast one circuit board 21 installed at the interior of the case 10while having a predetermined interval and a plurality of lightingemitting diodes (LED) 22 installed at the circuit board 21 while havinga predetermined interval from each other so as to emitting light into afront side of the circuit board 21, additionally, various light sourcessuch as a fluorescent lamp or a neon lamp, etc. may be applied.

The cover plate 30 is an element which hides the light source 20 andalso exits light entering the interior while diffusing the light to thewhole surface thereof. The cover plate 30 may be made of transparent orsemitransparent material having light transmission, such asPolycarbonate (PC), polymethylmethacrylate(PMMA),Methylmethacrylate(MMA), epoxy, Polyethylene Terephthalate(PET),Polyprophylene(pp), ABS resin, etc.

Also, as shown in FIG. 3, countless bubbles 31 for light scattering areformed at the interior of the cover plate 30. The bubbles 31 perform afunction for scattering light as well as a function for refracting lightpassing through the bubbles, differently from typical particles used inthe prior art, thereby improving diffusivity and also minimizingdecreases of light transmission.

The bubbles 31 may be formed by a foam forming method, such as a foamextrusion method or a foam injection method, etc., when the cover plate30 is manufactured.

The number and size (diameter) of bubbles 31 per unit volume, which areformed at the cover plate 30, have to be formed, considering diffusionand transmission. When the number of bubbles 31 per unit volume of thecover plate 30, i.e. inclusion rate is too high (over 35%), lightdiffusivity is superior, but light transmissivity is lowered, so thatbrightness decreases, and compression strength and tensile strength dueto bubbles remarkably decrease. On the other hand, as shown in FIG. 4,when the inclusion rate of bubbles of the cover plate 30 is too low(under 5%), the degree of light scattering is low so that diffusivityremarkably decreases and the cover plate can not properly perform adiffusion function, and intervals between bubbles are larger so that thelight source can be observed by naked eyes. Therefore, the cover plateis not suitable for a lighting fixture, particularly for anadvertisement fixture.

Also, when the size of bubbles 31 is too small (under 60 μm), lightdiffusivity is superior, but light transmissivity decreases so thatbrightness decreases. Also, as shown in FIG. 5, when the cover plate ismanufactured, it is very difficult to control the size of bubbles due tomechanical limitations, so that mass production thereof is actuallydifficult. On the other hand, in a case where the size of bubbles 31 istoo big (over 700 μm), although the bubbles has light diffusivity, thedirect light transmission area for direct transmission of incident orexiting light per unit bubble increases, so that the light source can befaintly observed by naked eyes (see the photograph of FIG. 6).

According to the present invention, so as to satisfy light transmissionas well as light diffusivity, and also achieve mass production andsuitability for an advertisement fixture, the cover plate 30 has bubbleinclusion rate of 5%˜35% and includes bubbles having a size within therange of 60 μm˜700 μm.

As described above, when the size of a bubble 31 is over 700 μm, thelight source is faintly observed by naked eyes so that the function ofthe cover plate as a cover of a lighting fixture remarkablydeteriorates. Meanwhile, when the size of a bubble 31 is smaller than 60μm, it is impossible to achieve mass production thereof.

Hereinafter, Table 1 shows a result of an experiment which is performedby using cover plates formed in the process below. Polyethyleneterephthalate (PEP) resin is inserted into the carbonic acid gas at asupercritical pressure state, and the pressure is dropped so as togenerate nuclei of bubbles. The generated nuclei of bubbles are foamedat a high temperature (100° C.) and cooled so as to form a cover plate.An light source used in the experiment is a light plate exiting lightemitted from a plurality of LEDs at an average illuminance of 2580 lux.Cover plates, which include bubbles having an average size (diameter) ofapproximate 300 μm, and have each different bubble inclusion rate, aredisposed on an upper side of an emitting surface of the light plate oneby one. Then, intensity of illumination, transmissivity, and diffusivityof light emitted through each cover plate are measured.

TABLE 1 light source LED light plate (average illuminance: 2580 lux)average size of bubbles 300 μm bubble inclusion rate Under 5% 5~20%20~35% over 35% intensity of 2,310 2,220 1,980 1,370 illumination (lux)light transmissivity 89.5 86.0 76.7 53.1 (%) light diffusivity low goodgood good possible to be employed impossible possible possibleimpossible in a lighting fixture

As shown in Table 1, in a case where the bubble inclusion rate of thecover plate 30 is within 5˜20%, and 20˜35%, cover plates have a superiorilluminance of 2,220 lux and 1,980 lux, respectively, and have aremarkably superior light transmissivity within 86.0% and 76.7%,respectively, in comparison with a conventional cover plate having alight transmissivity within 50%.

However, in a case where the bubble inclusion rate of the cover plate 30exceeds 35%, light diffusivity is very high, but light transmissivitydecreases so that illuminance remarkably decreases to 1370 lux.Therefore, the cover plate 30 is unsuitable to be employed in a lightingfixture.

Also, in a case where the bubble inclusion rate of the cover plate 30 isless than 5%, since distances between bubbles are big, the amount oflight directly transmitted is excessive so that light transmissivity ishigh, but light diffusivity remarkably decreases. Therefore, in thiscase, the cover plate is insufficient in achieving light diffusion sothat it is unsuitable to be employed in a lighting fixture.

Therefore, so as to employ the cover plate according to the presentinvention as a lighting fixture in a billboard, etc., bubble inclusionrate thereof has to be within the range of 5%˜35%, and the size of abubble has to be approximately 60˜700 μm.

As such, the cover plate 30 according to the present invention hasremarkably superior light transmissivity and superior illuminance incomparison with a conventional cover plate for a lighting fixture havingno bubbles or typical light plate for a liquid crystal display.

Also, the conventional cover plate has a low light transmissivity,within approximately 50%, so that illuminance thereof is low. Also,since the conventional cover plate uses inorganic particles such asoxytitanium, etc., the manufacturing cost thereof is high. Therefore,the conventional cover plate is unsuitable as a cover for a large-sizeadvertisement board or a lighting lamp.

However, the cover plate according to the present invention providessuperior light diffusivity and light transmission due to bubbles 31, andhas an advantage in mass production because of the reduced weightthereof and low manufacturing cost.

Meanwhile, the average size (diameter) of bubbles 31 formed at the coverplate 30 can increase or decrease from a light incident surface toward alight emitting surface. For example, bubbles 31 arranged at a sideadjacent to the light incident surface of the cover plate 30 can have asize smaller than that of bubbles arranged at a side adjacent to thelight emitting surface. In this case, the bubbles 31 of the cover plate31 can be observed by naked eyes, and when light is provided from thelight source, light progressing toward a front part of the cover plateis easily transmitted while meeting a large-sized bubble 31, so thatsuperior illuminance can be provided.

When the average size of bubbles 31 arranged at the front part of thecover plate 30 and the average size of bubbles arranged at the rear partthereof are different from each other, transmission is further improvedwhile diffusivity is kept.

FIG. 7 illustrates a cover plate according to another embodiment of thepresent invention. The cover plate 30 according to the second embodimenthas a structure where a pattern 32 having a polygonal (a triangularshape in this embodiment) prominence-depression shape is successivelyformed at a light incident surface facing an light source 20. Such apattern 32 may be a longish prism-pattern as shown in FIG. 8, or may bevarious other patterns, such as an embossing pattern of apolypyramid-shape or a hemisphere-shape.

The pattern 32 of the cover plate 30 increases a light receiving area soas to increase the amount of incident light and decreases reflexibility.Particularly, the cover plate 30 according to the second embodiment hasa larger light receiving area due to the pattern 32 in comparison with acover plate having a simple plane so that the area where light emittedfrom the light source 20 makes contact with light incident surface islarger. Accordingly, the amount of incident light increases, therebyfurther improving luminance.

FIG. 10 illustrates a cover plate according to the third embodiment ofthe present invention. The cover plate 30 according to the thirdembodiment has a dual-layer structure including a bubble layer 30 a anda light transmission layer 30 b. The bubble layer 30 a has apredetermined thickness and includes countless bubbles 31 used forscattering light at the interior thereof, and the light transmissionlayer 30 b, which is transparent and has a predetermined thickness, isintegrally formed at a rear surface of the bubble layer 30 a without aninterfacial surface. Therefore, there is an advantage in that a decreasein light transmissivity can be minimized in spite of an increase in thethickness of the cover plate.

As described above, bubbles 31 formed at the interior of the cover plate30 scatter and refract light, thereby increasing light diffusivity, andalthough the cover plate 30 has light transmission, a certain loss oflight is caused in comparison with a cover plate having an emptyinterior thereof in a transparent state.

Therefore, when the size of an advertisement fixture is larger and thesize of the cover plate is also larger, the thickness of the cover plateincreases together with the above increase so as to secure the ownstrength of the cover plate. As such, when the thickness of the coverplate 30 increases, the number of bubbles increases as much as theincrease of the thickness thereof so that the light transmissivitydecreases at a certain degree.

According to the third embodiment, when the cover plate 30 has adual-layer structure including a bubble layer 30 a having bubbles 31 anda light transmission layer 30 b having an empty interior thereof,although the thickness of the cover plate 30 increases, a decrease inthe light transmissivity is minimized while light diffusivity is kept atthe same level as the above-described cover plate according to the firstembodiment, so that lowering of luminance can be prevented.

At this time, it is preferable that an interfacial surface between thebubble layer 30 a and the light transmission layer 30 b does not exist.To achieve this, the transmission layer 30 b and the bubble layer 30 aare formed by the same synthetic resin, and the light transmission layer30 b and the bubble layer 30 a are formed by a scheme where syntheticresin including bubbles 31 and synthetic resin including no bubbles 31are stacked on each other in a paste state so as to integrally adhere toeach other.

Also, the thickness of the light transmission layer 30 b can be twotimes or three times as much as the thickness of the bubble layer 30 a,and according to the whole area of the cover plate 30 and a luminancelevel to be achieved, etc., the thickness of the bubble layer 30 a andthe light transmission layer 30 b can be freely varied.

As shown in FIG. 11, the cover plate 30 according to the thirdembodiment may also has a pattern 34 formed at a light incident surfacethereof so as to increase a light receiving area, similarly to the coverplate 30 according to the second embodiment.

The function of the pattern 34 is the same as the pattern 32 (refers toFIG. 4) of the above-described cover plate 30 according to the secondembodiment. Therefore, the description about the function will beomitted.

Meanwhile, although patterns 32 and 34 for increasing a light receivingarea are formed at each light incident surface of the cover plates 30 inthe above described embodiments, predetermined patterns (not shown) forsuppressing total internal reflection may be also formed at a lightemitting surface from which light is emitted.

FIGS. 12 and 13 illustrate a cover plate 30 applied to an advertisementfixture according to another embodiment. In the advertisement fixtureaccording to this embodiment, a resin plate 40 for secondary diffusionand an advertisement sheet 50 containing advertisement content arestacked at a front part of the cover plate 30 one by one, and a fixingchassis 60 of a square-shape, which is used to fix the resin plate 40for secondary diffusion and the advertisement sheet 50 respective to thecase 10, is assembled with the front part of the case 10.

Supporting members 70, which suppress warping or vibration, etc. casedby an increase of the size of the cover plate by supporting the coverplate 30 respective to the case 10, may be separately installed at theinterior of the case 10.

Although the resin plate 40 for secondary diffusion is preferably madein a white color, the resin plate can have another color, such asyellow, etc., and is also made from resin material having acharacteristic of light transmission, such as acryl. Also, it ispreferable that the resin plate 40 for secondary diffusion is formedseparately from the cover plate 30. Meanwhile, the resin plate 40 can bealso formed integrally with the cover plate 30 through a doubleinjection forming process, etc.

When the end part of the supporting member 70 makes complete contactwith the cover plate 30, light diffusion does not completely performedat an area where the supporting member 70 makes contact with the coverplate 30 so that a shadow can be observed at this area by an outerobserver.

Therefore, it is preferable that a front part of the supporting member70 is spaced a little from a rear surface of the cover plate 30.

Also, according to the above-described embodiments, although the coverplate according to the present invention is employed in an advertisementfixture such as a billboard, the cover plate for a lighting fixtureaccording to the present invention may also be employed in a cover of alighting fixture such as a cover of fluorescent lamp or a cover of astand, or in a case of a specific shape having an light source in theinterior thereof, e.g. a case of a fixture for an interior design havingan artistic configuration, such as a human or an animal, etc.

Although an exemplary embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

The cover plate for a lighting fixture according to the presentinvention can be employed in various lighting fixtures requiringillumination, such as an advertisement fixture, e.g. a billboard, aninterior lighting, a lighting fixture for an interior design, etc.

1. A cover plate for a lighting fixture, which is arranged at anexterior of an light source of the lighting fixture so as to exitlighting emitted from the light source outward, wherein the cover plateis made from light transmissive resin material having 5˜35% of bubblesfor light scattering, so as to diffuse and emit light emitted from thelight source through an entire surface of the cover plate
 2. The coverplate for a lighting fixture as claimed in claim 1, wherein the bubbleshave an average size within a range of 60 μm˜700 μm.
 3. The cover platefor a lighting fixture as claimed in claim 1, wherein an average size (adiameter) of the bubbles increases or decreases from a light incidentsurface to a light emitting surface.
 4. The cover plate for a lightingfixture as claimed in claim 1, wherein a pattern having a predeterminedprominence-depression shape is formed at a light incident surface facingthe light source.
 5. The cover plate for a lighting fixture as claimedin claim 4, wherein the pattern has a prism-shape, a polypyramid-shape,or an embossing shape, and is successively formed on a whole surface ofthe light incident surface.
 6. The cover plate for a lighting fixture asclaimed in claim 1, wherein the cover plate includes a bubble layer,which has a predetermined thickness and includes countless bubbles forlight scattering formed at an interior of the bubble layer, and a lighttransmission layer which is integrally formed on one surface of thebubble layer without an interfacial surface, has a predeterminedthickness, and includes no bubbles formed at an interior of the lighttransmission layer.
 7. The cover plate for a lighting fixture as claimedin claim 6, wherein a pattern of a predetermined prominence-depressionshape is successively formed at an outer surface of the lighttransmission layer.
 8. The cover plate for a lighting fixture as claimedin claim 6, wherein the light transmission layer is made of the samematerial as the bubble layer and adheres to one surface of the bubblelayer while being stacked on the surface of the bubble layer.
 9. Alighting fixture comprising: a case; an light source installed at aninterior of the case so as to emit light; and a cover plate installed atan outer side of the light source, the cover plate being made from lighttransmission resin material including bubbles for light scattering withthe inclusion rate of 5˜35%, so that the cover plate exits light emittedfrom the light source while diffusing the light to a whole surface ofthe cover plate.
 10. The light fixture as claimed in claim 9, furthercomprising a supporting member installed at an interior of the case soas to support a rear surface of the cover plate so that the cover plateis prevented from getting bent toward the light source.
 11. The lightfixture as claimed in claim 9, further comprising a resin plate forsecondary diffusion installed at a front surface or a rear surface ofthe cover plate, the resin plate being made from resin material havinglight transmission.
 12. The light fixture as claimed in claim 9, whereinbubbles of the cover plate have a diameter within a range of 60 μm˜700μm.
 13. The light fixture as claimed in claim 9, wherein a patternhaving a prominence-depression shape is formed at a light incidentsurface facing the light source.
 14. The light fixture as claimed inclaim 9, wherein the cover plate includes a bubble layer of apredetermined thickness having countless bubbles for light scatteringformed at an interior of the bubble layer and a light transmission layerof a predetermined thickness, which is integrally formed at one surfaceof the bubble layer without an interfacial surface and includes nobubbles formed at an interior of the light transmission layer.